bash-3.2$ cat hex2base64.pl6
#!/usr/bin/env perl6

my $hex = @*ARGS[0];
my $bin = pack 'H*', $hex;
bash-3.2$ ./hex2base64.pl6 '49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f757
3206d757368726f6f6d'
Cannot call 'Real'; none of these signatures match:
:(Mu:U \v: *%_)
  in any  at gen/parrot/BOOTSTRAP.nqp:1219
  in method Real at gen/parrot/CORE.setting:1032
  in method Real at gen/parrot/CORE.setting:3696
  in method Real at gen/parrot/CORE.setting:1032
  in sub infix:<%> at gen/parrot/CORE.setting:4188
  in sub infix:<%> at gen/parrot/CORE.setting:4185
  in block  at gen/parrot/CORE.setting:5526
  in sub pack at gen/parrot/CORE.setting:5496
  in block  at ./hex2base64.pl6:4